The present invention relates to a dental handpiece, in particular to a dental handpiece having a tool holder for detachably holding a dental treatment tool therein.
Dental handpieces have a tool holder for detachably holding a dental treatment tool therein. Two of such conventional dental handpieces with a tool holder are exemplified in FIGS. 6 and 8.
FIG. 6 is a sectional view of head 10 of an angle type dental handpiece having an air turbine. The head 10 accommodates rotor axis or bur sleeve 21, on which rotor 14 is fixed for rotatably driving the bur sleeve 21 by means of compressed air supplied from an external source. Coil spring 19 is introduced into the bur sleeve 21 and rests on a shoulder near the lower end opening 21a of the bur sleeve 21. Chuck member 40 is inserted into the bur sleeve 21 and contacts the upper end of the coil spring 19. There is a clearance between the inner surface of the bur sleeve 21 and the outer surface of the chuck member 40, which clearance is filled with inner tube 22 inserted from the upper end of the bur sleeve 21 and threadedly fixed on the inner surface of the bur sleeve 21. This inner tube 22 has a downwardly flared inner surface 22a in its lower end portion.
The chuck member 40 is shown in detail and partially exploded in FIG. 7. The chuck member 40 has upper tubular section 45 having a uniform outer diameter along its length, flaring section 44 having a downwardly increasing outer diameter, and annular section 41 having a uniform outer diameter. The upper tubular section 45, the flaring section 44, and the annular section 41 are formed integrally, with circumferential grooves 42 and 47 being interposed therebetween. The flaring section 44 has three axial slits 49 arranged at angular intervals. Each of these slits 49 receives a chucking die 43 of a complementary configuration.
In the bur sleeve 21, the chuck member 40 having the chucking dies 43 fitted in their corresponding slits 49, is biased upwardly by the coil spring 19, so that the outer surface of the dies 43 are contacted with the flared surface 22a. This flared surface 22a presses the dies 43 radially inwardly, so that the dies 43 press the periphery of a dental treatment tool 50 in the bur sleeve to hold the tool 50 in position.
In manufacturing the dental handpiece of the above structure, predetermined portions of the chucking member 40 should be cut away for forming the slits 49, and the corresponding dies 43 should be produced separately from the chucking member 40. Thus the dental handpiece of this type requires additional labor in producing separate parts and troublesome stock control of various parts. In assembling, this handpiece also requires additional labor in positioning the tiny dies 43 in the corresponding slits 49.
A chucking system including separate chucking dies fitted in corresponding slits in a chucking member to hold a dental treatment tool with these dies, is also disclosed in U.S. Pat. No. 4,595,363 assigned to the applicant of the present application.
FIG. 8 is a sectional view of a conventional dental handpiece of a straight type, wherein spindle 72 having coupling 84 at its proximal end is rotatably driven via the coupling 84 by means of a motor unit (not shown). The spindle 72 has an axial bore 72a in its distal portion for receiving dental treatment tool 90 therein. A plurality of apertures 72e communicating with the bore 72a are formed through the spindle 72 at angular intervals, and receive radially slidable pins 87 therein. A tubular member 75 is fitted around the spindle 72 slidably in the axial direction, and is distally biased by coil spring 78. The tubular member 75 has flared inner surface 75a in its distal portion for contact with the pins 87.
With this structure, since the tubular member 75 is distally biased by the spring 78, the flared surface 75a is brought into contact with the pins 75a in the spindle 72 to press the pins radially inwardly, so that the dental treatment tool 90 in the spindle 72 is held in position with these pins 75.
The dental handpiece of this type requires, however, production of separate tinypins 87, formation of apertures 72e, assembling of these parts, and stock control of various parts, which adds complexity and labor, as with the case of the handpiece of FIGS. 6 and 7.
The present invention aims to solve these problems in the prior art handpieces. It is therefore an object of the present invention to provide a dental handpiece, the number of which parts are minimized to eliminate problems in parts production and stock control. It is also an object of the present invention to provide a dental handpiece of which assembly is simplified compared to the prior art handpieces.
According to the present invention, there is provided a dental handpiece comprising:
a tool holder for receiving and detachably holding a dental treatment tool therein; and
a tubular compressor disposed around said tool holder, said tubular compressor having a flared inner surface along a portion of its length;
said tool holder and said tubular compressor being relatively slidable with respect to each other between a tool holding position and a tool releasing position,
wherein said tool holder has a plurality of presser tongues formed integrally with said tool holder, each of said presser tongues being partially separate from said tool holder with a slit to have a free tip and a connecting root with a reduced thickness,
wherein said flared inner surface of said tubular compressor elastically urges said tongues into pressure contact with said dental treatment tool to securely hold the tool in position, when said tool holder and said tubular compressor are in said tool holding position.
In the dental handpiece of the above structure, the presser tongues for securely holding a dental treatment tool in position are formed integrally with the tool holder simply by providing slits and reducing the thickness of the connecting root of the presser tongues. These presser tongues are elastically urged by the flared inner surface of the tubular compressor into pressure contact with the dental treatment tool, when the tool holder and the tubular compressor are in the tool holding position, to thereby securely hold the dental treatment tool in position. Thus no tiny dies or pins are required to be produced separately from the tool holder, and accordingly no assembling step of the dies or pins and the tool holder is needed. This remarkably simplifies production, stock control, and assembly of the parts, compared to the conventional dental handpiece.
In the tool holder of the above handpiece, the presser tongues may have a flared outer surface for snugly contacting with the flared inner surface of the tubular compressor.
The slits which partially separate the presser tongues from the tool holder may be of a U-shape. The tips of the presser tongues formed by the slits may be oriented in the direction of insertion of a dental treatment tool into the tool holder in use.
The tool holder may have a plurality of connecting portions also formed integrally with the tool holder, and positioned between the presser tongues in an alternate arrangement, and the outer surfaces of the connecting portions may be offset radially inwardly from the outer surfaces of the presser tongues, so that the connecting portions do not contact with the flared inner surface of the tubular compressor.
The tubular compressor may be made stationary, while the tool holder may be made slidable with respect to the tubular compressor. Alternatively, the tool holder may be made stationary, while the tubular compressor may be made slidable with respect to the tool holder.
In the former embodiment, the handpiece may have a spring for biasing the tool holder into the tool holding position, and a push button for contacting and sliding the tool holder into the tool releasing position against the biasing force of the spring, when the push button is pressed. In the latter embodiment, the handpiece may have a spring for biasing the tubular compressor into the tool holding position, and slidable releasing means for sliding the tubular compressor into the tool releasing position against the biasing force of the spring when the slidable releasing means is slid.
According to one embodiment of the present invention, the tubular compressor may be a bur sleeve having a flared inner surface along a portion of its length, or alternatively, having a tubular member with a flared inner surface along a portion of its length, fixed, for example by threaded fitting, on the inner surface of the bur sleeve. The tool holder may be a chuck slidably positioned in the bur sleeve. The bur sleeve may have a rotor fixed on its periphery for rotatably driving the but sleeve by means of compressed air, and may be rotatably supported by upper and lower ball bearings above and below the rotor.
According to another embodiment of the present invention, the tool holder may be a spindle connected to a coupling at its proximal end for receiving rotatable driving force from a motor unit, and may be rotatably supported by a ball bearing. The tubular compressor may be a slidable tube fitted on a part of the spindle slidably in the axial direction.